1. Field of the Invention
The present invention relates to an apparatus for producing mineral fibers, and more particularly refers to such an apparatus in which compressed air is utilized to form the fibers instead of conventionally used steam.
2. Description of the Prior Art
It has been conventional in the prior art to produce glass and mineral wool fibers by conveying a stream of molten material such as glass or slag onto a rotating surface. The molten material is thereby centrifuged into the path of a high velocity stream formed of super-heated steam, and the centrifuged material originally in the form of finely divided molten streams is blasted by the steam and formed into solidified material of fibrous form. Among the references which disclose this method are U.S. Pat. Nos. 2,869,175, 2,944,284, 3,013,299 and 3,022,538. However, the processes disclosed using steam have not been completely satisfactory, since, the relatively high velocity and impact force of steam causes an undesirable attenuation and severance or breakage of the mineral fibers, thereby reducing the efficiency of the apparatus and the quality of the finished product. Moreover, the use of steam requires rotor speeds of the centrifugal apparatus to be kept within critical limits in order to obtain filaments of a desired diameter. For example, where speed of the rotating disc is too high, the secondary attenuation produced thereby results in loose fibers which are too thin and frangible for normal use. Further, the fibers thus produced are of extremely short length and do not assume the structure of elongated threads or fibers. In order to overcome the deficiencies of steam operated fiberizing equipment, a method and apparatus are disclosed in U.S. Pat. No. 2,882,552 for using compressed air of low pressure to avoid the undesirable effects resulting from the use of high pressure steam. In the use of compressed air an advantage is realized in that no secondary attenuating defects are realized and the tendency to break or sever the filaments into short lengths are eliminated. However, the method and apparatus disclosed in that patent are not as efficient as desired and the quality of the mineral wool produced still leaves something to be desired with respect to the quality and the surface uniformity and smoothness of the finished fibers. Moreover, the apparatus disclosed in the patent is awkward to load and difficult to operate. The apparatus takes a lot of attention, is erratic, produces low yield and a high ratio of shot to fibers.
In U.S. Pat. No. 4,106,921, issued Aug. 15, 1978, of which applicant is one of the inventors, an apparatus for the low pressure air fiberization of mineral fiber is disclosed having an air plenum or housing with a central circular opening and defining a generally toroidal chamber. An annular slot is provided adjacent the circular opening for providing an air stream, and a duct is provided for transporting molten slag to the rotating cup. In an improved form a plurality of radial baffles are placed in the plenum around the central opening to provide uniform air flow to the annular slot. Additionally, as a further improvement, adjusting baffles are placed in the plenum to adjust the air flow for uniformity.
The present apparatus comprises an improvement over this apparatus resulting in raising the percentage of yield of fibers produced.